Welders and others wear shields or helmets to protect their faces and eyes from infrared, ultra-violet and part of the visible light emanating from the work area. To this end, the shields are provided with a viewing port which holds an eye-protecting light filter screen of a translucent material to filter light rays, particularly ultra-violet and infrared rays. Usually a relatively inexpensive clear glass or plastic is placed over the light filtering screen to protect the filter from flying sparks and molten metal such as encountered in welding.
Filter plate as used herein encompasses both panes of material, the one that filters radiation and the overlying protective glass or plastic plate which is generally used to protect the filter. Prior art filter plate holders are generally inserted into the welder's shield or helmet from the rear or interior by snap action and generally involve a mechanism whereby the filter plates are held against the inside of the helmet surface by spring retainer means.
Recent industry safety regulations impose more stringent requirements on eye-protecting devices such as welder's shields or helmets and require that they meet certain standards, particularly with respect to increased impact resistance. Filter plate holders which are inserted in shields or helmets from inside the helmet and held against the interior surface of the shield often do not meet the more stringent standards with respect to impact resistance.